Treatment of cellulosic fiber and composition therefor



2,91 1,326 Patented Nov.,3, 1959 '3 Claims. (Cl. 1171'39.4)

" Thisinvention relates to an improved process for treating cellulosic textiles to-impart thereto resistance to creas ing and similar effects. The. invention further deals with a novel composition of matter particularly adapted for the aforementioned treatments.

It. is an object. of this invention to provide a process for treating cellulosic. textiles, such as cottonv or regenerated cellulose, whereby to impart thereto durable calendering. effects, crease-resistance, shrink resistance and other similar effects utilizing a finish which is resistant to: chlorine retention. Chlorine-retention refers to the tendency of a given finish to form heat-unstable, chlorinecontaining compounds when the textile fiber bearing the finish: is treated in a hypochlorite bleaching bath. It. is

.anundesirable: quality of the finish, inasmuch as it tends to weaken the fiber.

A further object of this invention. is to provide a Y stable, marketable composition of matter adapted for the aforegoingpurposeso Other objects and achievements of thisfiinven-tion will. appear as the description proceeds.

In. copending application of Gastao l'rltrel, Serial No.

novel. compositions of matter are described. and claimed which consist essentially of concentrated (-0 to 70% by weight) aqueous. compositions of a condensation product. of formaldehyde with the dimethylether of di- United States Pflti tfOfifice "566,377 (Patent. No. 2,825,710, issuedMarch 4, 19-58),

methylol urea, said condensation product. consisting .pre-

dominant-1y of dimethylol-di(-methoxyrnethyl.)urea. Said compositions of matter have the-meritorious practical utility of endowing cellulosic textile fiber with durable calendering. effects, crease-proofing or shrink resistance, they are applied; to thefabric in. customary manner from a dilute aqueous bath, followed -bysqueezing, :drying. andcuringtlte fabricat temperatures above 105 C. (say 120 C. for 4 minutes). -very good fromv the viewpoints of immediate quality and durability to washin However, like all urea-formalde- 1 The effects are hyde condensates, these agents suffer from high chlorineretention. In other words, if fabric treated with these agents is treated in a hypochlorite bleaching bath, the. finish absorbs chlorine, which in turn. mayscorch the fabric upon ironing and may weaken it in tensile strength.

Now according to our invention-,the above bleachsensitivity of cellulosic fabric treated with dimethyloldi(methoxymethyl)urea is effectively overcome by carrying out the padding of the fabric with said agents in the presence of zinc nitrate and thencuring the fabric at the higher endof the temperature range customarily emplayed for such purposes,that isat about 300- to 350 F. Q-The above result is very surprising, inasmuch as we -know of no other instances where zinc nitrate eliminates the damage from chlorine-retention of a urea-formaldehyde type finish. Moreover, even with the particular finish under discussion, other zinc salts, for instance the chloride or sulfate, have been utterly ineffective as rezinc nit-rate to thepa'dding. bath from which the. resinous finish is,applied,.the quantity of. the. zinc nitrate added being suflicient. to. produce a concentration. thereof of between, 0.6 and. 4% by weight in the aqueous bath. Inasmuch as the fabric is generally squeezed to a: wet pick-up of 60. to 100%, the deposit of zinc nitrate onthe fiber will generally vary from 0.36 to 4% by weight. of the fiber. The concentration of. the di-methy1o1...compound, itself. in. the dilutedv pad bath is. ordinarilybetween 5 and. 10%. V

On. the other hand, we may add the zinc nitrate to the concentrated, marketable aqueous composition of the finishing agent, which generally contains from 5-0 to 70% by weight of said formaldehyde ditmethoxymethyl)urea condensate. In such event, the quantity of zinc nitrate added. should preferably be from 19.10 9% by weight of said marketable composition. I

- That such compositions could at .all. be prepared and marketed is again highly surprising, inasmuchaszinc salts, such as nitrate or sulfate, when added toother formaldehyde-urea condensates, for instance 1,3-bis(hydroicymethyl)-2-imidazolidone, cause considerable discoloration: of the product, often attended even by separation into layers. In the instant invention, however, the concentrated composition containing zinc nitrate as'above specified remained stable and clear for long periods'of time, throughout all the tests that we have conducted in this respect.

We do not know the explanationfor this unusual stability; nor do we know the reason why or how the zinc nitrate acts to prevent chlorine-retention by the finsh applied to cellulosic fiber.

Without limiting this invention, the following examples are given. to illustrate our preferred mode ofopera-t-ion. Parts mentioned are by weight.

Part I.'Preparafi0n of the finishing agent and the pad bath The preparation of concentrated,marketable aqueous compositions containing dimethylol'ditrnethoxymethyl)- urea is described in detail in said copending application G. Etzel, Serial. No. 566,377. A general outline. of this procedure is as follows:

At first, one mole of urea and two moles'o'f formaldehyde are reacted inan aqueoususolution ofS to 10 moles of methanol, at 65 to C; and at a pH of 7.5 to 9.

The reaction mass is then cooled to between 20'and 315 C. and acidified. to apH: of 4 to 5'. 'Itis then warmed to between=-35 and 45 C- to efiec-t etherification. xTEhe earth, andv the pH is adjusted". to between 7 and 8 by the addition of acetic acid. The solution is then filtered and the filtrate is adjusted to the desired concentration, normally 50 to 70% active ingredient as determined by nitrogen analysis.

. To provide the novel composition corms. invention it is merely necessary to add and dissolve zinczinitrate in jthe aqueOussOIution in sufiicientr amount to bring the composition within the limits defined above, i.e., to contain about 50 to 70% by weight, on an active ingredient basis, of dimethylol-di(methoxymethyDurea and about 19 to 9% by weight of zinc nitrate. The zinc nitrate may be added either just before or after the clarification step. The zinc nitrate is normally added as its hydrate, since this form is readily available commercially.

The composition thus obtained is a clear, water-white liquid and is ready for use. It is quite stable to storage without discoloration or decomposition.

To prepare the padding bath, it is merely necessary to dilute the above composition down to the concentration required for the pad bath, say, to contain to of the dimethylol-di(methoxymethyhurea. The textile fabric is then padded with this solution to obtain 60 to 100% wet pick-up (3 to 10% pick-up on a dry basis),

but generally 70% wet pick-up. The amount of zinc nitrate in the pad bath will be between about 0.6 and 4% depending, of course, upon its amount in the concentrate.

Alternatively, the zinc nitrate may be added to the diluted pad bath instead of the concentrated, marketable composition of the finishing agentj Insuch event, the catalyst (i.e. the zinc nitrate) is added in quantity corresponding to between 0.6 and 4% based on the weight of the bath.

In either of the above cases, the fabric is padded in the pad bath, squeezed to a 60 to 100% pick up, dried at about220 F., and then cured at about 300 to 350 F. for about 1 to 5 minutes, the time varying inversely with temperature. The fabric is then scoured with a solution of about .05 of a detergent and about 0.1% of soda ash, rinsed and dried. The treated cotton is found to have good crease resistance; it is also shrink resistant and when calendered before curing the calender effect is durable to washing.

It is recommended that both the temperature and the time of curing should be held within the limits stated. For example, if temperatures much below about 300 F. are used, excessive amounts of zinc nitrate are re quired to obtain a significant improvement. This can be overcome somewhat by longer curing times, but the 8 to 11, by adding further quantity of soda ash from time to time if necessary. The excess alkalinity is then washed out in the final rinsing step prior to drying.

Part II.Detailed procedure of treatment and testing Impregnation and curing-A number of pad baths were prepared by adding 36 parts of an aqueous solution of dimethylol-di(methoxymethyl)urea (70% active ingredient) to 464 parts of water, and stirring the mixture thoroughly. The baths therefore contained 5% by weight of the active ingredient of the treating resin. Then a 10% solution of zinc nitrate hexahydrate was added to each bath in amounts varying to give desired concentrations ranging from 0.6 to 4% zinc nitrate in the solution by weight.

A strip of cotton fabric was padded through each of the above baths at room temperature, making two dips and two nips. The treated fabrics were then air dried, and cured in a hot-air oven at temperatures ranging from 300 F. for 5 minutes to 350 F. for 1 minute. The treated fabrics were then neutralized by the following procedure:

Neutralization.-A solution containing .01% soda ash and 0.05% commercial surface active agent consisting of a mixture of long chainalkyl sodium sulfates was prepared in 2000 parts of water. The solution was heated to to F., and the cured fabrics were immersed therein and allowed to remain until they were completely wet out. The fabrics were then removed, passed through a wringer, rinsed in warm water (110 to 120 F.), and ironed dry on a flat press iron. The fabrics were then kept for 4 hours or more at about 70 F. and 65% relative humidity, prior to testing.

Testing procedure.--For each of the fabrics above prepared, a fresh sodium hypochlorite bath was prepared by diluting a commercially available, 5% sodium-hypochlorite solution with distilled water to obtain 0.25% of available chlorine. The pH of each solution was'adjusted to between 9 and 10 with sodium bicarbonate or sodium carbonate.

Each fabric sample was first pre-wetted in distilled water at F., then cooled and transferred to one of the above hypochlorite' baths, which were maintained at about 77 F. After proper impregnation according to a standardized mechanical procedure, each sample was wrung out, rinsed, dried and submitted to a scorching test at 365 F. for 30 seconds. Tensile strength measurements were then applied side-by-side with a watercontrol, that is a piece of impregnated and cured fabric which was given a similar treatment as the bleach and scorch test, but employing an aqueous bath containing no hypochlorite whatever.

Results.-It was found that where the fabric was cured at 300 F. for 5 minutes, there was no perceptible drop in tensile strength compared to the control, provided the initial impregnation bath contained from 1.9 to 4% by weight of the catalyst (zinc nitrate). Where the curing was done at 325 F. for 1.5 minutes or at 350 F. for 1 minute, satisfactory results were obtained with as low as 0.6% catalyst content.

We claim as our invention:

1. A process for producing crease-resistant effects upon cellulosic textile fiber, which comprises padding the same in an aqueous bath comprising dimethylol-di- (methoxymethyl) urea and zinc nitrate, then drying the fabric, curing the same at a temperature of 300 to 350 F. andthen scouring with a mildly alkaline solution.

2. A process as in claim 1, the concentration of the reagents in said pad bath being such that, after squeezing, the pick up on the fiber is from 3 to 10% by weight of dimethylol-di(methoxymethyl)urea and from 0.36 to 4% by weight of zinc nitrate, said percentages being based on the weight of the fiber.

3. A composition of matter adapted for use as a treating agent for cellulosic textiles, which comprises an aqueous solution of (1) a condensation product of formaldehyde with the dimethyl ether of dimethylol urea, said condensation product consisting predominately of dimethylol-di(methoxymethyl)urea and being present in said composition in a concentration betweenabout 50 and 70% by weight, and (2) zinc nitrate, said zinc nitrate beingpresent in said composition in a concentration between about 19 and 9% by weight.

References Cited in the file of this patent UNITED STATES PATENTS Etzel Mar. 4, 1958 

1. A PROCESS FOR PRODUCING CREASE-RESISTANT EFFECTS UPON CELLULOSIC TEXTILE FIBER, WHICH COMPRISES PADDINGS THE SAME IN AN AQUEOUS BATH COMPRISING DIMETHYLOL-DI(METHOXYMETHYL) UREA AND ZINC NITRATE, THEN DRYING THE FABIC, CURING THE SAME AT A TEMPERATURE OF 300* TO 350* F. AND THEN SCOURING WITH A MILDLY ALKALINE SOLUTION. 